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  Installing Trim-Tilt switch on Dash Panel for Mercury Outboard Engine

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Author Topic:   Installing Trim-Tilt switch on Dash Panel for Mercury Outboard Engine
skred posted 11-21-2012 10:21 AM ET (US)   Profile for skred   Send Email to skred  
The motor is a 1998 Mercury40. The trim-tilt on the throttle handle has broken and fallen out and lost. Right now, I can jump the center and either of the other 2 contacts in the handle socket with a short wire and the trim-tilt will work. I'd like to find and tap into the 3 wires that lead to the original missing handle switch.
I want to put a control for t&t on the dash. I have the 3-position toggle (momentary - off - momentary). Looking "under the hood", I can see the green and blue leads going to the t&t unit. Can I tap into those two leads and run them to the switch I'm installing, adding a 12v hot lead (red)to the center pole on the switch? I'm not sure if tapping in after the relays will damage them.
To complicate matters, the throttle control has a "pigtail"{?) connector hanging out of the shift-throttle assembly, unconnected to anything. (looks like 5 pins, plus a single wire outside the connector. I can see a gray wire, and cannot see the others. I suspect this is a dash connector for tach and several other things. I cannot find a schematic for these things. I started to open the throttle control, but stopped for fear I may not be able to get it back together. Ideas-solutions?
jimh posted 11-21-2012 10:33 AM ET (US)     Profile for jimh  Send Email to jimh     
In the TRIM circuit the normal color code is

BLUE = UP (remember blue sky is up)

GREEN = DOWN (remember green grass is down)

The power is usually provided on a circuit that has 12-Volts even when the IGNITION key is in the OFF position.

If the other connector is for connecting a tachometer, there are probably circuits in that connector for +12-Volts via the IGNITION key switch (in RUN position) and Common (battery negative).

I don't have any speculation what the other two pins of the five-pin connector might be used for.

skred posted 11-21-2012 11:22 AM ET (US)     Profile for skred  Send Email to skred     
Thanks, Jim. My primary concern is if I tap into the blue and green wires leading from the motor to the pump, will I be bypassing some sort of relays? If so, would I damage the relays by testing the connection I would like to make?
jimh posted 11-21-2012 12:40 PM ET (US)     Profile for jimh  Send Email to jimh     
You can wire your new switch in parallel with the existing switch. The electrical circuit will not be able to tell which switch closed the circuit. Just don't hit the UP button on one switch and the DOWN button on the other at the same time.
skred posted 11-21-2012 04:08 PM ET (US)     Profile for skred  Send Email to skred     
Jim, that's precisely my problem. I can't intercept the wires from the switch on the motor, nor the wires in the throttle control. The only place I find the blue & green wires in the open - is leading out of the large covered electrical shield on the side of the engine, and they lead directly to the pump. I understand that there may be up and down relays "upstream" in the circuit before these wires lead to the pump. If I could be sure that tapping those 2 leads would not somehow damage the up and down relays which are probably on the other side of these 2 wires, I'd go ahead. If I'm wrong about relay damage, I'd be incurring a substantial repair bill for new relays...
Perhaps I can take a chance and try and find the wires leading to the motor from the throttle control... It would involve dis-assembling the throttle-shift control, and I'm not too excited about doing that.
jimh posted 11-21-2012 11:44 PM ET (US)     Profile for jimh  Send Email to jimh     
You need to put the switch in the relay coil circuit. Not in the actual trim pump circuit. The switches must control the relay coils, not the pump motor.
skred posted 11-22-2012 10:57 AM ET (US)     Profile for skred  Send Email to skred     
That's the info I needed. Thanks! Now I have to hunt down the pre-coil leads... Appreciate the help, Jim.
skred posted 11-23-2012 10:15 AM ET (US)     Profile for skred  Send Email to skred     
Found the solution. As you said, Jim, I figured out it was a simple matter of releasing the motor tilt switch retaining clip, exposing the 3 wires. Simply tapped into them, ran the new wires to the dash switch and reinstalled the motor tilt switch. Presto. Appreciate the help.

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